/*
 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
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 */
package javax.swing;

import java.awt.event.*;
import java.util.Vector;
import java.util.Enumeration;
import java.io.Serializable;

/**
 * This class is used to create a multiple-exclusion scope for a set of buttons. Creating a set of
 * buttons with the same <code>ButtonGroup</code> object means that turning "on" one of those
 * buttons turns off all other buttons in the group. <p> A <code>ButtonGroup</code> can be used with
 * any set of objects that inherit from <code>AbstractButton</code>. Typically a button group
 * contains instances of <code>JRadioButton</code>, <code>JRadioButtonMenuItem</code>, or
 * <code>JToggleButton</code>. It wouldn't make sense to put an instance of <code>JButton</code> or
 * <code>JMenuItem</code> in a button group because <code>JButton</code> and <code>JMenuItem</code>
 * don't implement the selected state. <p> Initially, all buttons in the group are unselected. <p>
 * For examples and further information on using button groups see <a
 * href="https://docs.oracle.com/javase/tutorial/uiswing/components/button.html#radiobutton">How to
 * Use Radio Buttons</a>, a section in <em>The Java Tutorial</em>. <p> <strong>Warning:</strong>
 * Serialized objects of this class will not be compatible with future Swing releases. The current
 * serialization support is appropriate for short term storage or RMI between applications running
 * the same version of Swing.  As of 1.4, support for long term storage of all JavaBeans&trade; has
 * been added to the <code>java.beans</code> package. Please see {@link java.beans.XMLEncoder}.
 *
 * @author Jeff Dinkins
 */
@SuppressWarnings("serial")
public class ButtonGroup implements Serializable {

  // the list of buttons participating in this group
  protected Vector<AbstractButton> buttons = new Vector<AbstractButton>();

  /**
   * The current selection.
   */
  ButtonModel selection = null;

  /**
   * Creates a new <code>ButtonGroup</code>.
   */
  public ButtonGroup() {
  }

  /**
   * Adds the button to the group.
   *
   * @param b the button to be added
   */
  public void add(AbstractButton b) {
    if (b == null) {
      return;
    }
    buttons.addElement(b);

    if (b.isSelected()) {
      if (selection == null) {
        selection = b.getModel();
      } else {
        b.setSelected(false);
      }
    }

    b.getModel().setGroup(this);
  }

  /**
   * Removes the button from the group.
   *
   * @param b the button to be removed
   */
  public void remove(AbstractButton b) {
    if (b == null) {
      return;
    }
    buttons.removeElement(b);
    if (b.getModel() == selection) {
      selection = null;
    }
    b.getModel().setGroup(null);
  }

  /**
   * Clears the selection such that none of the buttons
   * in the <code>ButtonGroup</code> are selected.
   *
   * @since 1.6
   */
  public void clearSelection() {
    if (selection != null) {
      ButtonModel oldSelection = selection;
      selection = null;
      oldSelection.setSelected(false);
    }
  }

  /**
   * Returns all the buttons that are participating in
   * this group.
   *
   * @return an <code>Enumeration</code> of the buttons in this group
   */
  public Enumeration<AbstractButton> getElements() {
    return buttons.elements();
  }

  /**
   * Returns the model of the selected button.
   *
   * @return the selected button model
   */
  public ButtonModel getSelection() {
    return selection;
  }

  /**
   * Sets the selected value for the <code>ButtonModel</code>.
   * Only one button in the group may be selected at a time.
   *
   * @param m the <code>ButtonModel</code>
   * @param b <code>true</code> if this button is to be selected, otherwise <code>false</code>
   */
  public void setSelected(ButtonModel m, boolean b) {
    if (b && m != null && m != selection) {
      ButtonModel oldSelection = selection;
      selection = m;
      if (oldSelection != null) {
        oldSelection.setSelected(false);
      }
      m.setSelected(true);
    }
  }

  /**
   * Returns whether a <code>ButtonModel</code> is selected.
   *
   * @return <code>true</code> if the button is selected, otherwise returns <code>false</code>
   */
  public boolean isSelected(ButtonModel m) {
    return (m == selection);
  }

  /**
   * Returns the number of buttons in the group.
   *
   * @return the button count
   * @since 1.3
   */
  public int getButtonCount() {
    if (buttons == null) {
      return 0;
    } else {
      return buttons.size();
    }
  }

}
